|  
               Differences              | 
          
           
             | 
          
          
            | There is no game select screen  | 
          
          
            | There are no game options  | 
          
           
            | The right difficult switch selects between one and two player mode  | 
          
          
            | The left difficulty switch freezes/unfreezes the battleship in place  | 
          
           
            | The score counters are non-functional  | 
          
           
            | There are more types of enemies than in the final version  | 
          
          
            | The enemies never reach the second players shield | 
          
           
            | The sounds are very different (and quite nasty)  |